Secondary Emission Mass Spectrometer (SEMS) is designed and assembled. It is anticipated that the facility will contribute to research programs in a number of Institutes, specifically NIMH (S.Markey) and NHLBI (H.Fales). The SEMS has the following features: (a) Ultra-high vacuum chamber with ultimate vacumbetter than 10 to the minus 9 torr; (b) Rapid linear motion multi-specimen holder permitting reflection and transmission mode of operation; (c) Energy analyzed ion gun (.05-10 keV) with deflector, pulser, and rastering. The gun is switchable to ions only or neutrals only modes of operations; (d) SIMS mass spectrometer in both reflected and transmission SIMS; (e) MS/MS/collision cell double quadrupole tandem system, (f) Secondary electron emission cell for negative ion studies; (g) Electron bombardment gun (.05-1.5 keV); (h) Flexible multi-flange system which will allow testing of various designs of ion sources and ion guns. The SEMS permits us to study secondary emission processes on various surfaces under bombardment by electrons, ions, and neutrals in connection with ionization of biological compounds of high molecular weight. Development of analytical techniques based on Particle Induced Ionization Mass Spectrometry using SEMS for peptide sequencing analysis is planned for FY l982-l983.